Solutions to Towler & Sinnott Chemical Engineering Design 2nd edition
Part I: Process Design Part II Plant Design
Chapter 1: Introduction Chapter 13: Equipment design
Chapter 2: Flowsheet development Chapter 14: Pressure vessel design
Chapter 3: Utilities and energy recovery Chapter 15: Reactor design
Chapter 4: Process simulation Chapter 16: Separation processes
Chapter 5: Process control Chapter 17: Multistage columns
Chapter 6: Materials of construction Chapter 18: Solids handling processes
Chapter 7: Estimating capital costs Chapter 19: Heat transfer equipment
Chapter 8: Estimating costs of production Chapter 20: Plant hydraulics
Chapter 9: Economic analysis
Chapter 10: Safety
Chapter 11: Plant layout and environmental impact
Chapter 12: Optimization
Note that most of the problems involve design and so have no single unique answer. Credit should be
given to students who have followed the right method and found similar solutions. Indeed, the
probability of any student independently coming up with the exact answers given in the solution set for
more than a few problems should be vanishingly small and this event should cause the grader to be
suspicious. The “optimal” solutions presented are usually not numerically optimal and are merely close
enough to optimal to be good enough for engineering purposes. This reflects the optimization
philosophy described in Chapter 12.
When teaching design, I usually do not give the teaching assistants prepared solutions to the homework
problems. I find that if they have to work through the problems themselves they are much better
prepared to help the students. They are usually not too happy about it, but it does them good and builds
character.
1
,Chapter 1
Problem 1.1
There are many possible correct answers to this question and it can be answered in varying levels of
detail. The key steps that should be included for each process with typical required times are listed
below. The project plan can be sketched using a spreadsheet or drawn up using a project planning tool
such as MS Project (as in Problem 1.2).
a) A petrochemical process using established technology, to be built on an existing site. Since the
technology is established, there will be no need to generate design concepts and carry out R&D.
The steps are then:
Set design basis (1 week)
Evaluate economics, optimize and select design (typically 10-30 weeks, depending on project
scope)
Detailed design and equipment selection (typically six months to one year)
Procurement and construction (typically one year)
Shakedown and start-up (typically one month)
These steps are usually more or less sequential, although some procurement of long lead-time
items may be started during detailed design.
b) A process for full-scale manufacture of a new drug, based on a process currently undergoing pilot
plant trials. Since the pilot plant is already operating the designer already has a good idea of the
process flowsheet and the goal is to be prepared to ramp up production to full scale once the drug
is approved. The steps are:
Set design basis (1 week)
Confirm performance/scale-up of pilot plant operations (2-20 weeks, depending on how
smoothly pilot plant runs)
Optimize and select design (10-20 weeks)
Detailed design and equipment selection (about six months)
In parallel to these process design activities there will be activities related to getting approval for
the new drug:
Conduct clinical trials (6 months to 2 years)
Review clinical trial results (typically 3 to 6 months)
Obtain FDA approval
Some of the procurement and construction activities will be started as soon as the first clinical
results look promising, but final construction and shakedown will not occur until the review of
clinical trials is completed.
c) A novel process to convert cellulosic waste to fuel. The technology and flowsheet will need
considerable development, so a schedule might be:
Set design basis (1 week)
Generate design concepts & carry out R&D (one to five years)
Evaluate economics, optimize and select design (six months, but could run parallel to
generating design concepts for up to five years)
Detailed design and equipment selection (six months to one year)
Procurement and construction (about one year)
Shakedown and start-up (one month to one year, as there may be start-up hiccups with a new
technology)
d) A spent nuclear fuel reprocessing facility. There is established technology for nuclear fuel
reprocessing, but new processes are always possible. For an established technology the schedule
would look much like problem (i) and for new technology it would look like problem (iv). All of
the steps would probably take longer because of the scale of the plant and additional steps would
be needed for obtaining local, state and federal permits and revising them after setting the design
basis, selecting the design, and completing detailed design. The time taken to obtain permits could
be several years and the total time to operation would probably exceed ten years.
e) A solvent recovery system for electronics production. This is a relatively small project, so the steps
would be:
Set design basis (1 – 2 days)
Generate design concepts (1 to 2 months)
Evaluate economics, optimize and select design (ten weeks or less)
Detailed design and equipment selection (2 to 3 months)
Procurement and construction (3 to 6 months)
Shakedown and start-up (one month)
2
, Problem 1.2
This requires a more detailed breakdown than problem 1.1. A sample project plan is given in the
lecture slides and shown below (in MS Project format):
Suitable intermediate deliverables could include:
The design basis
A completed PFD (or PFD review)
A completed process simulation
A completed PID (or review)
Problem 1.3
a) The list of product requirements will be somewhat qualitative and depend on the preferences
of the “customer” group. The required properties of the dough must consider properties of the
dough itself, as well as properties of the final (home-baked) product. Some properties of the
dough that might be considered include:
• Shelf life
• Calorie content
• Chocolate chip content
• Stiffness (do you scoop it or is it preformed in cookie shapes?)
• Baking time
Properties of the end cookies are perhaps more obvious:
• Chewiness
• Crunchiness
• Sweetness
• Saltiness
• Mouth feel
• Serving size (if pre-formed)
b) The product specifications could include the following:
• Composition of major ingredients (see any cookie dough: flour, fat or oil, water, etc.)
• Composition of chocolate chips
3
Part I: Process Design Part II Plant Design
Chapter 1: Introduction Chapter 13: Equipment design
Chapter 2: Flowsheet development Chapter 14: Pressure vessel design
Chapter 3: Utilities and energy recovery Chapter 15: Reactor design
Chapter 4: Process simulation Chapter 16: Separation processes
Chapter 5: Process control Chapter 17: Multistage columns
Chapter 6: Materials of construction Chapter 18: Solids handling processes
Chapter 7: Estimating capital costs Chapter 19: Heat transfer equipment
Chapter 8: Estimating costs of production Chapter 20: Plant hydraulics
Chapter 9: Economic analysis
Chapter 10: Safety
Chapter 11: Plant layout and environmental impact
Chapter 12: Optimization
Note that most of the problems involve design and so have no single unique answer. Credit should be
given to students who have followed the right method and found similar solutions. Indeed, the
probability of any student independently coming up with the exact answers given in the solution set for
more than a few problems should be vanishingly small and this event should cause the grader to be
suspicious. The “optimal” solutions presented are usually not numerically optimal and are merely close
enough to optimal to be good enough for engineering purposes. This reflects the optimization
philosophy described in Chapter 12.
When teaching design, I usually do not give the teaching assistants prepared solutions to the homework
problems. I find that if they have to work through the problems themselves they are much better
prepared to help the students. They are usually not too happy about it, but it does them good and builds
character.
1
,Chapter 1
Problem 1.1
There are many possible correct answers to this question and it can be answered in varying levels of
detail. The key steps that should be included for each process with typical required times are listed
below. The project plan can be sketched using a spreadsheet or drawn up using a project planning tool
such as MS Project (as in Problem 1.2).
a) A petrochemical process using established technology, to be built on an existing site. Since the
technology is established, there will be no need to generate design concepts and carry out R&D.
The steps are then:
Set design basis (1 week)
Evaluate economics, optimize and select design (typically 10-30 weeks, depending on project
scope)
Detailed design and equipment selection (typically six months to one year)
Procurement and construction (typically one year)
Shakedown and start-up (typically one month)
These steps are usually more or less sequential, although some procurement of long lead-time
items may be started during detailed design.
b) A process for full-scale manufacture of a new drug, based on a process currently undergoing pilot
plant trials. Since the pilot plant is already operating the designer already has a good idea of the
process flowsheet and the goal is to be prepared to ramp up production to full scale once the drug
is approved. The steps are:
Set design basis (1 week)
Confirm performance/scale-up of pilot plant operations (2-20 weeks, depending on how
smoothly pilot plant runs)
Optimize and select design (10-20 weeks)
Detailed design and equipment selection (about six months)
In parallel to these process design activities there will be activities related to getting approval for
the new drug:
Conduct clinical trials (6 months to 2 years)
Review clinical trial results (typically 3 to 6 months)
Obtain FDA approval
Some of the procurement and construction activities will be started as soon as the first clinical
results look promising, but final construction and shakedown will not occur until the review of
clinical trials is completed.
c) A novel process to convert cellulosic waste to fuel. The technology and flowsheet will need
considerable development, so a schedule might be:
Set design basis (1 week)
Generate design concepts & carry out R&D (one to five years)
Evaluate economics, optimize and select design (six months, but could run parallel to
generating design concepts for up to five years)
Detailed design and equipment selection (six months to one year)
Procurement and construction (about one year)
Shakedown and start-up (one month to one year, as there may be start-up hiccups with a new
technology)
d) A spent nuclear fuel reprocessing facility. There is established technology for nuclear fuel
reprocessing, but new processes are always possible. For an established technology the schedule
would look much like problem (i) and for new technology it would look like problem (iv). All of
the steps would probably take longer because of the scale of the plant and additional steps would
be needed for obtaining local, state and federal permits and revising them after setting the design
basis, selecting the design, and completing detailed design. The time taken to obtain permits could
be several years and the total time to operation would probably exceed ten years.
e) A solvent recovery system for electronics production. This is a relatively small project, so the steps
would be:
Set design basis (1 – 2 days)
Generate design concepts (1 to 2 months)
Evaluate economics, optimize and select design (ten weeks or less)
Detailed design and equipment selection (2 to 3 months)
Procurement and construction (3 to 6 months)
Shakedown and start-up (one month)
2
, Problem 1.2
This requires a more detailed breakdown than problem 1.1. A sample project plan is given in the
lecture slides and shown below (in MS Project format):
Suitable intermediate deliverables could include:
The design basis
A completed PFD (or PFD review)
A completed process simulation
A completed PID (or review)
Problem 1.3
a) The list of product requirements will be somewhat qualitative and depend on the preferences
of the “customer” group. The required properties of the dough must consider properties of the
dough itself, as well as properties of the final (home-baked) product. Some properties of the
dough that might be considered include:
• Shelf life
• Calorie content
• Chocolate chip content
• Stiffness (do you scoop it or is it preformed in cookie shapes?)
• Baking time
Properties of the end cookies are perhaps more obvious:
• Chewiness
• Crunchiness
• Sweetness
• Saltiness
• Mouth feel
• Serving size (if pre-formed)
b) The product specifications could include the following:
• Composition of major ingredients (see any cookie dough: flour, fat or oil, water, etc.)
• Composition of chocolate chips
3
